Nesting Behavior

The Great horned owl is by far the most common owl in the Americas; they derive their name from the plumicorns on their head that resemble horns. We have been studying a family of great horns. We have never seen the two (male and female) together but we know they are a nesting pair. We can tell the difference between the sizes of the birds, the male great horned is much smaller then the female.  Another way we can tell the difference is the male’s call is far deeper. We have heard him calling to the female as well as to the bothersome crows that flock to the female.

Since these two are nesting pairs I felt some basic nesting information was in order.

·         Usually breeds late Jan-early Feb.- we heard mating calls from this pair in late December

·         Has an average of 2-5 eggs (30-37 days to hatch)- this particular pair had two chicks in 2011

·         The young hang around nest 2.5 months after they have left mothers protection.

The female currently has eggs in the nest. They should be hatching any day now. Just to get an idea of daily activities, we set up some cameras. The following show some of our data:

           

            05 Feb 2012

·         18:03- female leaves nest

·         18:15- female returns to nest

            06 Feb 2012

·         6:03- owl leaves nest

·         6:04- owl returns

·         8:14- crows disturb nest

·         4 crows arrive at nest at 9:03, stayed until 9:32

·         Crows return at 9:49, leave at 9:50

·         Crows return at 10:38, leave at 10:41

·         Crows return at 12:45, leave at 12:48

·         Multiple crows at 14:14, video ends at 14:38

17 Feb 2012

·         Owl leaves nest at 18:10

·         Returns at 18:13

18 Feb 2012

·         Movement at 7:48, too foggy to tell what exactly

·         Crow activity at 10:1, settles down at 10:20

·         Owl leaves at 18:05pm

·         Returns at 18:12pm

24 Feb 2012- We took a scope out to actually see what the owl was doing and where she was going when she leaves the nest.

·         18:22- female left nest and flew across creek into another section of woods

·         18:35- she returned to nest

·         Crow disturbs nest at 8:14am

These movements cause us to ask several questions. First of all, where is she going? Is she going to get food from the male? Where exactly is the male hanging out? With great-horns, the males will sometimes take turns sitting on the eggs. We have not observed this behavior. We will continue to gather data after the eggs hatch. Hopefully, we will be able to answer some of these questions. We would like to eventually be able to better understand the nesting habits of these owls. Perhaps if we can better understand their needs and behaviors, then we may be able to protect them.

Female peering over the edge of the nest.



One of the chicks from 2011.



Two chicks from 2011 with the mother behind them.

Check out the following two cameras:

Great Horned cam1

Great Horned cam2

Signs of Spring?

Upland Chorus Frogs (Pseudacris feriarum) have a variation of color palettes, but commonly brown to grey with a pinkish cast. Adults range from 0.75 inches to 1.5 inches, with females usually being slightly larger than males. They are often hard to track to a precise location because the pitch of the call echoes in their common locations. They are often found in moist woodlands, river bottom swamps, ponds, bogs, and marshes. They are most active immediately after hard rains and at night. This is most common during the breeding season, between November and March (depending on temperature and rainfall), and much more difficult in the non-breeding season. The females lay approximately a thousand eggs at a time, attached to vegetation, during this season.

We conducted an experiment on the calls of the Upland Chorus Frogs stemming mainly from our own curiosity. We measured how close a potential predator (us) could get to the frogs before they stopped calling and when they began calling after the perceived threat moved on. We found that a small water hole, which is actually a water runoff site, gave us our best chance to collect some data. During the first trial, we were able to get within 20’7” before frogs stopped calling. They resumed their chirping 8.6s after we moved on. The second trial had the frogs ceasing at 16 feet, taking 5 min. 10s to resume. The third test had the frogs stopping at 15’11” and starting back at 4 min. 55s. The fourth and final test resulted in the frogs stopping at 21’ and resuming after 9 min. 8.6s. The frogs seemed to sense the danger the more times we enacted the test.

There is no known research that has measured how close potential predators could get before these frogs stop calling. There did not seem to be a definite pattern as to when they stopped calling. However, the time it took them to resume after we had walked by did increase. Were they just annoyed that we kept “bothering” them or did they really think we were a danger. We did try this study at another marshy location that is considerably larger and could not get the frogs to stop calling. Is this because of the size of the frog population in that area?  Is there strength in numbers? Could the larger groups be less afraid of potential predators? How can simple little frogs sense when danger is near? These questions may drive us to perform more experiments in the near future.

The following shows some additional information on these frogs:

http://www.carolinanature.com/herps/chorusfrog.html

Owl Update

Last year's Barred owl female. Was this the victim?

We went to look for owl pellets and whitewash in an attempt to study the barred owl pair. We have not been able to find them near last year’s nest. The beginning of our walk was overcast and storms threatened. We began our search and almost immediately came across an area of feathers with two wings that looked like they had been pulled from the bird’s body. The wings were surrounded by feathers concentrated into a small circular area. We then searched the woods around the feathers for the remaining bird, but could not find anything. The feathers looked like they had not been disturbed since the kill had taken place. They were not scattered around as if another animal had been through the area. It appeared as if whatever had taken the body had simply flown away with it.  

Pile of feathers and wing.

Bird found within 4 feet of dead owl.



Fresh whitewash near last year's nest.



A few feet from the feathers, the body of a smaller bird was lying with its head completely detached. Across the trail, underneath a tree, one of the members of the class found some whitewash, evidence that an owl had been in the area. It was originally guessed that the wings we had found belonged to a red-tailed hawk. One of the guys in the class did some research and found that the wing pattern matched that of a barred owl. In reviewing the pictures, I looked up the wing pattern on a feather identification website and agree that they were feathers of a barred owl. All these findings pose many questions. What was able to so violently pull the wings off a barred owl? Where did the rest of it go? We do know that one of the only natural predators of a barred owl, the great horned owl, lives in the area. Did it feel threatened and kill the barred owl? And what was the smaller bird’s role in this mid-air drama, if that’s what it was? I’d like to find some of the answers to these questions but we may not be able to.

Is this the culprit?

Signs of Intelligence

Procyon lotor, the northern raccoon, is an interesting animal found all over Statesville. Raccoons are usually nocturnal and omnivorous, meaning they are equal opportunists when it comes to eating. The percentage of invertebrates, vertebrates, and plants that they consume are almost evenly distributed. At the greenway, we have seen raccoon tracks along the bank of the creek, crossing the trail, along the trail, and all over the woods. We even saw raccoon tracks around a dead, red-bellied woodpecker that had been plucked.

We put up two trail cameras for a month, and raccoons were in 85% of the pictures. Two of the pictures raised some questions. One picture shows four raccoons crawling around a tree. This was a picture from one of our non-baited stations. What makes it interesting is the fact that before the 1990’s, raccoons were thought to be mainly solitary animals. Recent studies have shown that females that are related sometimes meet at feeding grounds. Research also shows that males sometimes set up their own “bachelor pads” to defend their territory against outsiders.



Four raccoons hanging out. You can see the back of the fourth at the bottom of the picture.

The other picture was taken at a bait station. We placed a whole NY strip in a suet feeder cage and attached it to a tree. We got pictures of this particular raccoon climbing the tree, sniffing the meat, and the next picture showed that the steak was gone while the suet cage remained. How did the raccoon do it? Did he pull the steak through the cage? Not likely. Did he open the suet and then close it? Maybe he broke the steak into small enough pieces so that he could then pull them out. If he did this, he had to do it within a minute because the camera was set to have a one minute delay between shots.

Raccoon and empty suet feeder.

I heard one story recently where a raccoon took a suet feeder from a tree one night only to return the empty cage the next night to the base of the tree. It is safe to say that raccoons are very intelligent. Surprisingly, intelligence studies among raccoons are lacking. Some show that their learning speed is equivalent to the rhesus macaques, and another shows that they can remember solutions to problems for an extended period of time. There is a lot we do not know about these mammals. The one thing we do know is that they certainly are thriving along the greenway trails.

Hide and Seek?



I recently visited the great horned owl's nest to see if I could detect any evidence the owl is hanging around again. Last January, an owl used this abandoned crow's nest to raise two chicks. When I got under the nest, I heard a crow begin to "bark" really loud. It took me about ten seconds to spot him in a tree fifty feet from the nest. He was clearly agitated. Within thirty seconds, two more crows arrived. One dove straight into a pine as seven more crows arrived from the North. I immediately saw the female great horned fly out of the tree and into the nest. She ducked for cover in the nest as the crows continued to call loudly.



If you were a crow could you see the owl?



Mobbing behavior is common among crows. They often will chase hawks or owls from tree to tree. I watched this same owl get chased from six different trees over a period of twenty minutes last January before landing in the nest. We have also seen crows dive down and nip at this owl with their beaks as she perches. The literature suggest that they do this to protect themselves and their young or potential young. Researchers have even shown that crows will begin to display this behavior within several minutes after being exposed to just a stuffed owl in a tree.

On this particular day it took ten minutes for the crows to leave the area around the nest. One crow came back twice and called before leaving for good. It makes one wonder whether the crows just got tired and gave up or did they actually forget about the owl. Was this a friendly game of "hide and go seek" or were the crows trying to teach the owl a lesson? If the latter is true, this owl is a slow learner.

We discovered the owl on the nest for the next several days, which indicated she probably already has eggs.